1. Field of the Invention
The invention relates to an apparatus for treating contaminated liquid, and more particularly to an apparatus including a fluid bed reactor and an apparatus for dissolving a gas, such as oxygen, into the liquid entering the reactor.
2. Reference to Prior Art
In many processes it is desirable to dissolve gases in liquids. In one such process an apparatus for dissolving oxygen in water is employed in a water treatment system for removing fuel constituents from water contaminated thereby. The apparatus for dissolving oxygen in water, or "oxygenator", includes a bubble contactor into which oxygen and a stream of contaminated water are introduced to dissolve the oxygen in the water. To safeguard against the build-up of a potentially combustible mixture of fuel constituents and gaseous oxygen, the bubble contactor is provided with auxiliary equipment. This equipment includes recirculation equipment including an eductor circuit to recirculate undissolved oxygen and a vent circuit to purge undissolved gas in excess of that which the recirculation equipment can accommodate. The vented gas can include significant amounts of oxygen which is expensive to produce. Following "oxygenation", the contaminated water is biologically treated in a fluid bed reactor in which the water is passed through a bed of particulate solids serving as a substrate for microorganisms. The microorganisms consume, under aerobic conditions, the fuel constituents in the water. The principles of operation of fluid bed biological reactors are provided in the following U.S. patents: U.S. Pat. No. 4,202,774 issued May 13, 1980 to Kos; U.S. Pat. Nos. 4,009,098, 4,009,099 and 4,009,105 all issued Feb. 22, 1977 to Jeris; and U.S. Pat. No. 3,956,129 issued May 11, 1976 and U.S. Pat. No. 3,846,289 issued Nov. 5, 1974, both to Jeris et al.
Another example of the use of an oxygenator is provided in U.S. Pat. No. 4,477,393, issued Oct. 16, 1984 to Kos. This oxygenator is employed in a treatment process to denitrify waste water. To pressurize the water in order to increase the rate and extent of oxygen dissolution the oxygenator is installed below ground, beneath a hydrostatic head.
Further examples of apparatus for dissolving gas in liquid are provided in U.S. Pat. No. 4,466,928 issued Aug. 21, 1984 to Kos and in U.S. Pat. No. 3,926,588 issued Dec. 16, 1974 to Speece. The Speece patent discloses a pressurized gas transfer system for dissolving oxygen in water. The Speece gas transfer system includes parallel pipe circuits through which water is alternately pumped into a conically-shaped bubble contactor. Gas bubbles containing oxygen are introduced into the bubble contactor to oxygenate the water.
In prior art arrangements, all of the liquid which is to be treated is first passed through an oxygenator and the oxygenator and associated equipment are sized accordingly to handle large flow rates.